U.S. Pat. No. 6,416,321 and the corresponding European Patent EP 0 834 291 B1 disclose a dental handpiece of the before mentioned kind which comprises a gripping sleeve that is provided with an integrated powder container for storing a predetermined amount of powder as an abrasive material for the polishing or cleaning of teeth in the course of a singular treatment of teeth. The powder container is substantially cup-shaped and forms the rearward end of the gripping sleeve with which it is coaxially screw-connected at an enlarged portion of the gripping sleeve. The gripping sleeve is branched at its enlarged portion under an acute angle with respect to its longitudinal axis for providing a coupling connection for a common supply means for air and water at a rearward end of the gripping sleeve. Pressurised air is supplied to the powder container via a first supply line while water is supplied via a second supply line to a multiple nozzle arrangement which is provided at a forward spray head of the gripping sleeve. A transfer line for powder mixed with air connects the powder container with this multiple nozzle arrangement. For avoiding a backflow of the powder particles that are taken up within the powder container by the pressurised air which is supplied by the common supply means for air and water via the first supply line there is also provided a one-way valve means which with the design of a ball valve forms a functional part of the coupling connection. The ball valve is arranged in an insert member forming the connecting end of the first supply line for pressurised air in such manner that it will prevent any backflow of the pressurised air from the powder container back to the coupling connection for avoiding any contamination of its different coupling parts by the abrasive powder particles that will accompany such backflow.
U.S. Pat. No. 5,857,851 and its corresponding European Patent EP 0 870 477 B1 disclose a dental handpiece of a similar design and provided with an integrated powder container that is formed as a closed hollow body of rotation acting as a whirl chamber spatially in all directions. The powder container is arranged substantially at half length of a gripping sleeve which at its axial rearward end is provided with a coupling means of a turbine in-line quick coupling of a common supply means for air and water. A first supply line for pressurised air comprises a tubular piece which is connected to the powder container. A second tubular piece serving as a transfer line for powder mixed with air connects the powder container with a multiple nozzle arrangement at a forward spay head of the gripping sleeve. A second supply line for water is further connected to the same multiple nozzle arrangement.
German Patent Publication DE 101 13 289 A1 discloses a dental spray device. A separate powder reservoir is interconnected with a supply line for pressurised air and connects via a transfer line for powder mixed with air to a dental handpiece having a multiple nozzle arrangement at a forward spray head of a handle. A supply line for water is further connected to the same multiple nozzle arrangement. The supply line for pressurised air is provided at a position upstream of the powder reservoir with a condensate separator and a one-way valve that are arranged in series and serving the purpose of supplying only dry air to the powder reservoir.